The formation water present in subterranean geologic formations of oil, coal, and other carbonaceous materials is normally considered an obstacle to the recovery of materials from those formations. In coal mining, for example, formation water often has to be pumped out of the formation and into remote ponds to make the coal accessible to mining equipment. Similarly, formation water has to be separated from the crude oil extracted from a subterranean field and disposed of typically underground. The extraction, separation and disposal of the formation water add costs to recovery processes, and generate a by-product regarded as having little value.
Further investigation, however, has revealed that even extracted formation water can support active communities of microorganisms from the formation. The presence of these microorganism in the formation environment were known from previous recovery applications, such as microbially enhanced oil recovery (MEOR), where the microorganisms naturally generate surface active agents, such as glycolipids, that help release oil trapped in porous substrates. In MEOR applications, however, it was generally believed that the microorganisms were concentrated in a boundary layer between the oil and water phases. The bulk formation water was believed to be relatively unpopulated, because it lacked a hydrocarbon food source for the microorganisms. More recent studies have shown that robust populations of microorganisms do exist in the bulk formation water, and can even survive extraction from the geologic formation under proper conditions.
The discovery of active populations of microorganisms in bulk formation water has come at a time when new applications are being envisioned for these microorganisms. For years, energy producers have seen evidence that materials like methane are being produced biogenically in formations, presumably by microorganisms metabolizing carbonaceous substrates. Until recently, these observations have been little more than an academic curiosity, as commercial production efforts have focused mainly on the recovery of coal, oil, and other fossil fuels. However, as supplies of easily recoverable natural gas and oil continue to dwindle, and interest grows using more environmentally friendly fuels like hydrogen and methane, biogenic production methods for producing these fuels are starting to receive increased attention.
Unfortunately, the techniques and infrastructure that have been developed over the past century for energy production (e.g., oil and gas drilling, coal mining, etc.) may not be easily adaptable to commercial-scale, biogenic fuel production. Conventional methods and systems for extracting formation water from a subterranean formation have focused on getting the water out quickly, and at the lowest cost. Little consideration has been given to extracting the water in ways that preserve the microorganisms living in the water. Similarly, there has been little development of methods and systems to harness microbially active formation water for enhancing biogenic production of hydrogen, methane, and other metabolic products of the microbial digestion of carbonaceous substrates. Thus, there is a need for new methods and systems of extracting, treating, and transporting formation water within, between, and/or back into geologic formations, such that microbial activity in the water can be preserved and even enhanced.
New techniques are also needed for stimulating microorganisms to produce more biogenic gases. Native consortia of hydrocarbon consuming microorganisms usually include many different species that can employ many different metabolic pathways. If the environment of a consortium is changed in the right way, it may be possible to change the relative populations of the consortium members to favor more combustible gas production. It may also be possible to influence the preferred metabolic pathways of the consortium members to favor combustible gases as the metabolic end products. Thus, there is also a need for processes that can change a formation environment to stimulate a consortium of microorganisms to produce more combustible biogenic gases.